Sets an asynchronous callback for actionable MediaCodec events. If the client intends to use the component in asynchronous mode, a valid callback should be provided before MediaCodec.Configure(MediaFormat, Android.Views.Surface, Android.Views.Surface, Android.Views.Surface) is called. When asynchronous callback is enabled, the client should not call MediaCodec.GetInputBuffers, MediaCodec.GetOutputBuffers, MediaCodec.DequeueInputBuffer(long) or MediaCodec.DequeueOutputBuffer(.BufferInfo, System.Int64).

Also, MediaCodec.Flush behaves differently in asynchronous mode. After calling flush, you must call MediaCodec.Start to "resume" receiving input buffers, even if an input surface was created.

[Android Documentation]